Raman scattering study of adsorption/desorption of water from single‐walled carbon nanotubes

Abstract

We utilized Raman spectroscopy to investigate H 2 O adsorption in and desorption from single-walled carbon nanotubes (SWCNTs). SWCNT tips were opened by known chemical methods and H 2 O was inserted into the tubes via capillary action over periods up to 136 h. The wavenumbers in the OH bending region of H 2 O increase almost exponentially with H 2 O treatment time. Following H 2 O adsorption for 136 h, Raman spectra were also measured as a function of heat-treatment temperature. These data lead to 0.07 eV for the H 2 O desorption energy from SWCNTs.

Water molecule encapsulated in carbon nanotube model systems: effect of confinement and curvature

“…The increment of about 0.014 Å in bond distance, although seems to be negligibly small, can have pronounced effect on the vibrational spectra of water. For encapsulated water, vibrational spectroscopy [33][34][35][36][37][38] is a sensitive indicator to probe the confinement effect as well as the strength and orientation of hydrogen bonding. It is well known that lengthening of the bond leads to a decrease in the stretching frequency, and thus, it is expected that the O-H stretching frequency in confined water will have a red shift as compared to that of the free water molecule.…”

Application of water–activated carbon isotherm models to water adsorption isotherms of single-walled carbon nanotubes

“…NMR techniques were also used to estimate water adsorption isotherms on oxidized SWNTs [11] and reveal the importance of functional groups in clustering of water molecules around the ends and defects of SWNTs. Raman spectroscopy [12] was recently used to study the adsorption of water on closed and open-ended SWNTs and to calculate the desorption energy of water molecules from the internal volume of nanotubes.…”

Effect of Water Filling on the Electronic and Vibrational Resonances of Carbon Nanotubes: Characterizing Tube Opening by Raman Spectroscopy

“…1). By comparing with the predicted values [14] for the RBM frequency and the excitation energy in the studied range, we can identify the second electronic transitions of the following semiconducting tubes: (9,7), (10,5), (11,3), and (12,1). Their chiral angles range from nearly armchair (n,n) to almost zigzag (n,0) (diameters, D, and chiral angles, a, listed in Table 1).…”

“…In Figure 3 the resonance excitation profile (REP) of empty and water-filled (10,5) tubes are shown together with the fit obtained with Equation 2. Other REP line shapes have been considered in literature, assuming band-to-band transitions, that is, uncorrelated electrons and holes, for which the square root of both terms in Equation 2 should be taken.…”

“…Raman scattering of H 2 O vibrations and the tangential modes of CNTs indicate adsorption/desorption of water on CNTs, however no quantitative information on the CNTs could be obtained. [10] Very recently, Longhurst and Quirke [11] calculated that filling of CNTs with water would lead to an upshift of the radial breathing mode (RBM) of the CNTs by 2-6 cm -1 . Here, we show that the RBM resonant Raman features of empty and water-filled SWCNTs can be very well resolved, even in measurements on bulk solutions, provided the nanotubes are solubilized using bile salt surfactants.…”